Two studies featured in the current issue of the Canadian Journal of Cardiology have shown that a new training program for reading electrocardiograms and designed for emergency medical service technicians (EMS) to evaluate patients with chest pain and accelerate treatment for ST-segment elevation myocardial infarction (STEMI), a serious form of heart attack, has provided excellent results and should become standard of care.

Leading researcher, Robin A. Ducas, MD, of Manitoba University in Winnipeg, Canada said:

“It’s well established that morbidity and mortality in myocardial infarctions is directly related to the duration of ischemia, and delays in restoring the flow of blood to the heart of even 30 minutes have been associated with an increase in mortality. By training EMS to administer and interpret ECGs at the scene, with oversight from an on-call physician, we demonstrated that we could achieve benchmark times from first medical contact to treatment.”

A 2005 audit of hospitals in Manitoba revealed earlier that according to the standards established by leading heart associations, including the Canadian Cardiovascular Society, only 14% of patients were given drugs to dissolve blood clots (thrombolysis) within 30 minutes from the first medical contact, with just 11% of patients receiving primary percutaneous coronary intervention (PPCI, or angioplasty) within the first 90 minutes of medical contact.

The issue was addressed by developing a system of pre-hospital ECG interpretation and triage. EMS are now provided with additional training in performing ECGs and interpreting their results for signs of STEMI. As soon as an EMS suspects a STEMI, he or she transmits the ECG to the on-call physician via the hand-held device for confirmation. When the physician confirms a STEMI, he or she directs the EMS to start pre-hospital thrombolysis (PHL) or to alert the hospital’s PPCI laboratory to prepare for the patient’s arrival.

By transmitting ECGs and through the real-time conversation between physician and EMS, false positive test results for STEMI are lower. The system also improves resource allocation by lowering the use of the catheterization laboratory when it is not actually needed. In positive cases, the emergency room is bypassed, with patients being directly transferred to the hospital’s cardiology department or the PPCI laboratory. If the physician diagnoses that the ECG is negative for STEMI (PHENST) the patients will be transferred to the nearest emergency room.

The study involved an evaluation of 380 cases from July 2008 to July 2010 in which from a total of 226 STEMI positive patients, 70% received PPCI, 21% were given PHL, and 20% had a coronary angiography without revascularization. The average time from first medical contact to treatment in the PHL treatment group was established as 32 minutes, with an average time of 76 minutes in the PPCI group. 41% of patients in the PHENST group were transferred to a hospital capable of PPCI and 59% were transferred to one of the six other hospitals in the system, which presented more often outside of normal catheterization laboratory hours. Of all patients, 44% were diagnosed with acute coronary syndromes, which included 7 cases of missed STEMI, and a higher mortality rate.

Dr. Ducas explained:

“The adoption of similar strategies in other urban areas could allow for achievement of guideline times, particularly for PPCI and regardless of the time of day. Transfer of patients with suspicious but negative ECG for STEMI (PHENST) to hospitals with comprehensive cardiac care may be warranted, and deserves further consideration.”

The team examined 703 cases that were evaluated by EMS in a related study, of which the EMS evaluated 323 cases as negative for STEMI and therefore did not transmit to the on-call physician. The results revealed that on arrival at the nearest emergency room, 52% of patients were diagnosed with “nonspecific chest pain” and subsequently discharged, whilst one case of STEMI was missed, and 2 other patients developed STEMI after arriving at the hospital. After an evaluation by a physician, 25% had a cardiovascular diagnosis.

The EMS evaluated 380 patients’ ECGs as positive and transmitted the results to the on-call physician, who subsequently suspected 226 cases of STEMI, 96.9% of which were confirmed. In only 7 from 226 cases, the catheterization lab was falsely activated and in 7 cases the physician missed the diagnosis.

Dr. Ducas points out: “The high level of false positives is a concern, given the risk of treatment. We do not have a clear guide as to what are acceptable levels of false positives and negatives. However, we have found both in the literature and in our own study that EMS pre-hospital ECG interpretation is fast, reliable, and plays a pivotal role in the care for patients with STEMI.”

Robert C. Welsh, MD, FRCPC, FAHA, FACC, from Alberta University’s Department of Medicine, and the Mazankowski Alberta Heart Institute in Edmonton, Alberta, Canada, writes in an editorial accompanying the articles:

“Our colleagues describe a program which provides the optimal platform to advance STEMI care in Canada. Although this approach is dependent on a motivated group of physicians willing to invest additional time and energy to deliver enhanced STEMI care, it allows pre-hospital confirmation of diagnosis, individual patient risk stratification, immediate decision regarding the optimal mode of reperfusion, and expansion of optimal systems of care to rural patients.”

Written by Petra Rattue